1. Field of the Invention
This invention relates to the field of antivibration isolation devices for machines, and in particular, to the field of elastic supports for motor vehicles.
It relates to the family of these elastic supports which exhibit great flexibility, improving the filtering of high vibration frequencies, where the risk of resonance at the characteristic frequency of the suspended masses is avoided by the hydraulic damping function integrated into the device.
The invention is adapted in particular to an arrangement in current use, in particular in power units of the transverse type in front-wheel drive vehicles, where at least one of the suspension points of said assembly is a cylindrical elastic part, force fitted by a tube which is an integral part of it, in a socket made either in a housing, or in a support installed, during assembly, on the power unit, and traversed by a shaft which makes possible fastening to the frame by a flange, or by means of a cantilever bolt.
2. Description of the Prior Art
The prior art shows that the geometry of revolution easily makes it possible to put, between rigid elements, a bonded elastomer which provides radial rigidity and acts as a gradual stop from a free zone of great flexibility of several millimeters to a controlled elasticity, but one which is, for example, five times higher, over a linear distance which is even shorter.
This controlled elasticity is necessary to react to the motor torque and to the motor braking in the two directions in which the power unit swings.
Devices using this geometry make it possible, by means of the use of appropriate cells, to obtain different flexibilities in the three directions, on one hand, and variations of the radial rigidity, on the other hand, variations due to the closing of these cells, which ensure high flexibilities and, consequently, the low suspension frequencies required for good antivibration filtering. Such devices are described, for example, in French Patent No. FR 2,335,744 (Citroen) and French Patent No. FR 2,441,101 (Nissan).
French Patent No. FR 2,551,161 (Tokay Rubber) proposes an elastic sleeve coupling, filled with fluid, where a revolving sleeve comprises two opposite chambers and a fluid circulation damped by passage through orifices, as well as an internal stop which limits radial travel.
The above-mentioned patents are incorporated herein by reference as if the entire contents thereof were fully set forth herein.
In addition, axially flexible mountings consisting of conical springs enclosing a hydraulic damping chamber have been improved, in particular, by the use of a long column of inertial liquid which, at low frequency, increases the apparent rigidity. Such devices are described in continuation FR 2,462,618 and French Patent No. FR 2,443,615 and European Patent No. EP 027,751 by Peugeot and Citroen.
An analysis of the prior art shows, apparently, that there are not hydraulic damping devices specifically adapted to a particular frequency and associated with a geometry of revolution.